It has been known in the food and pharmaceutical arts to provide an oxygen scavenger in product packaging in order to prolong the usable life of the food or pharmaceutical. A difficulty with the utilization of oxygen scavengers that are transition metal based and activated by protic solvents such as water is that they must be kept inactive until the time of packaging by keeping them dry (usually below 50% RH) and then must be rapidly activated by contacting a water source. Activation by water vapor available from the product to be packaged in many instances is too slow to guarantee rapid deoxygenation of the package to protect an oxygen sensitive product. Another difficulty is that if the oxygen scavenger is in contact with water, but not in contact with significant oxygen, hydrogen may be generated, which is undesirable as the bags of oxygen adsorbent swell.
Iron based oxygen scavengers are used in packaging bags of packaged meat for long distance shipping and other retail meat packaging to extend the freshness of meat. Iron and other transition metal powders generally require a protic solvent (usually water) to trigger the oxygen scavenging process. Traditionally, this moisture is obtained from the ambient environment that the oxygen scavenger is placed in. However, there are instances where in oxygen absorber would be placed in a relatively dry environment, or it is desired to be fully active upon the point of insertion to provide the most efficient oxygen removal, as is the case in the meatpacking industry. In those instances, a moisture source is usually packaged with iron to accelerate the reaction. Inorganic salts (electrolytes, acidifying agents, etc.) are usually mixed with iron powder in order to promote oxidation reaction. Given the lack of oxygen (to protect its reactive capacity during scavenger storage), this process inevitably generates hydrogen gas via reaction of the metal with water, which is undesirable in the operation. On the other hand, while the addition of buffer systems to increase the pH of mixture and impede hydrogen formation could minimize the production of hydrogen gas, it inevitably results in slower scavenging rates which is undesirable. It is ideal to allow the scavenging reaction to take place at the time of food packaging to maximize the scavenging rate, to fully utilize its reactive capacity, and to prevent hydrogen formation.
One of the current methods involves the preparation of iron and salt blends and a moisture regulator in one mixture and vacuum packaging the sachets. A prior art described a method of water or salt solution injection into premixed packaged iron/salt composition. This approach involves a complicated setup of a water injection device for the scavenger packets and packaging master bags. The setup is often costly, prone to malfunction and not flexible to operational changes. Therefore, it is desirable to find a way to provide timely activation of the inactive scavenging composition to speed up the scavenging reaction at the time of scavenger use.
The DelDuca et al. U.S. Pat. Nos. 5,928,560, 6,315,921, 6,508,955, 6,666,988, 6,926,846, and 7,147,799 disclose a system for injecting an aqueous solution into a oxygen scavenging packet and a system for breaking a capsule containing an aqueous solution in an oxygen absorbing packet. Rapid uncontrolled release of an aqueous solution into a scavenging formulation given low oxygen environment during packaging operations often results in hydrogen gas formation.
There remains a need for a method of preventing early hydrogen formation in oxygen absorbers utilizing water activated oxygen scavengers.